In a conventional ink-jet printer, ink is deposited on record media via a traveling printhead which propels ink drops onto the record media as it passes thereacross. The record media is spaced from the printhead, the upper surface of the record media being held at a predetermined minimum distance from the printhead (D.sub.m). Most printers set distance (D.sub.m) using a platen which supports the record media, the platen generally being held in a fixed position relative to the printer's printhead. The distance between the printhead and platen is defined as the record media gap. This gap must accommodate the passage of record media therethrough without smearing, but spacing should be kept to a minimum so as to maximize the quality of print. Consequently, the platen is set at a distance from the printer's printhead which is approximately equal to the nominal record media thickness plus the desired printhead-to-medium spacing (D.sub.m).
A problem arises, however, where different types of record media are used, particularly where such record media are of differing thicknesses, or where the different record media experience differing degrees of curl. This situation most commonly arises in ink-jet printers where both paper sheets and envelopes are to be printed on. Envelopes, it will be appreciated, are of a different thickness than paper sheets due to multiple paper layers, and experience increased curl due to the flap and adhesive used. These factors impact on the printhead-to-medium spacing and consequently impact on the overall quality of print. For example, where thicker record media is used, the risk of ink smear is increased. Although the risk of ink smear may be decreased by expanding the record media gap, such an expanse would impact negatively on the accuracy of ink dot placement due to the increase in distance to be traveled by the ejected ink.
One solution to this problem involves the adjustment of the record media gap whenever a new form of record media is used. In the past, this has involved operator-directed adjustment of the printer's printhead or platen, an adjustment which requires complex mechanism and which requires the operator to remember that an adjustment must be made. Printers employing known solutions have therefore been characterized by increased complexity and correspondingly by increased cost. Also, these printers may require an increase in the nominal printhead-to-medium spacing due to increased tolerances involved. This can result in a consequential derogation in the quality of print. There is thus a need for a new solution which addresses the problems associated with printing on record media of different types.